Many attempts have been made to retain and analyze waveform data associated with display systems, such as oscilloscopes and the like. The development of the storage cathode ray tube permitted waveforms to be displayed on an oscilloscope screen for extended periods of time; however, this system lacked versatility. A "split-screen" technique increased the capability by permitting two waveforms to be viewed simultaneously in any combination of stored and non-stored operating modes. To analyze these waveforms, or to perform any mathematical functions thereon, it was necessary for the operator to simulate the waveforms on paper and mentally calculate the desired results. For example, to obtain an electrical power curve from voltage and current waveforms, the tedious operation of point-by-point multiplication of the corresponding points on the voltage and current waveforms was performed, from which the points of the power waveform could be obtained. A major disadvantage of storage cathode-ray tubes for waveform analysis is that information stored thereon can be held for only a limited time. If a particular waveform was needed beyond the storage time limit, it became necessary to photograph such waveform or provide a facsimile.
One form of waveform processing was developed which was capable of categorizing waveform information on one axis only, usually the vertical axis. This system digitized the information and stored it in a memory bank, such as a core memory or a memory register. This information was then available to the display system on a recall basis to provide a refreshed display. However, this system also had its limitations, and one major disadvantage was its extremely narrow bandwidth capability. The system was locked to a timing signal or clock signal which was compatible to a computer and the single-axis information was processed at that rate. Because of slow sweep speeds required to display such processed information, it was impractical to simultaneously view real-time signals which were generally occurring at higher frequencies. While two or more such single-axis signals could be processed in this manner, which could include manipulation by a computer or the like, another serious disadvantage to previous systems was that due to differences in sweep timing and linearity, etc. the identical initial conditions could not be repeated, rendering the accuracy of such processed waveforms questionable and unreliable.